The present invention relates generally to bulk material handling apparatus and more particularly to a vertically adjustable, telescopic chute for delivery of granular, bulk material such as coal or the like to a delivery site. The use of telescopic chutes for the loading or delivery of granular materials is well-known and advantageous since they are capable of handling high tonnage throughputs while minimizing, to a degree, airborne dust generation. Use of a telescopic chute in delivering sized, granular coal to the storage yard of a power plant, for example, is common, wherein the chute is telescopically extended a vertical distance of over eighty feet from the delivery end of a conveyor device. As the height of the coal pile increases, the telescoping segments of the chute are incrementally raised and sequentially nested to maintain the delivery end of the lowermost chute segment in a spaced relation to the pile. In this manner, the lower end of the chute is not buried in the rising pile, and the shape of the pile may be controlled.
Heretofore, certain structural characteristics have caused difficulties in the operation of telescopic chutes. In prior chutes of this type, the wire ropes or cables used for hoisting are attached to the sidewall of the lowermost chute segment by outwardly extending, laterally mounted pulley arms. As the chute segments are raised, the lowermost segment with the pulley arms bears the total weight of the nested segments. This loading on the laterally extending arms causes the cross-sectional shape of the lowermost segment to become oval-like which naturally results in a binding condition in the upper chute segments which are to be nested as the chute is raised. The location of the pulleys or sheave wheels along the sides of the lowermost segment also results in the center of gravity of the nested segments being near the rotational centerline of the sheave wheels as the segments are being nested thereabove. This center of gravity problem causes instability of prior telescopic chutes due to the fact that the nested segments tend to become easily misaligned axially as the chute is raised, thus making nesting more difficult.
The present invention solves the problems found in prior chute devices by providing a telescopic chute in which the cross-sectional shape of the lowermost segment remains circular during raising operations to thereby eliminate the prior binding problems. In addition, the telescopic chute of the present invention provides a lifting structure which transfers the bearing weight of the chute segments from the lowermost chute to a separate structural bracing member so as to greatly improve the operation of the chute while minimizing costly maintenance. Still further, the telescopic chute of the invention provides an improved sheave wheel support structure which stabilizes the center of gravity of the nested chute segments relative to the hoist ropes to improve axial nesting alignment of adjacent segments as the chute is being raised.
While telescopic chutes limit dust generation compared with totally unenclosed conveyor dumping, such chutes still produce a significant amount of dust during operation, particularly where the granular material is free falling from heights greater than fifty feet or more.
The present invention further provides a telescopic chute including a novel dust collection system to further reduce the escape of airborne particulates.